<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .content{
        width: 100%;
        float: left;
    }
    .main{
        height: 200px;
        background: greenyellow;
        margin-left: 200px;
        margin-right: 200px;
    }
    .right {
        width: 200px;
        height: 200px;
        background: red;
       float: right;
       margin-left: -100%;
    }
    .left {
        width: 200px;
        height: 200px;
        background: red;
        float: left;
        margin-left: -100%;

    }
</style>
<body>
    <div class="content">
        <div class="main"></div>
    </div>
    <div class="left"></div>
    <div class="right"></div>
</body>
</html>